WO2005032390A1

WO2005032390A1 - Robot-assisted medical treatment device

Info

Publication number: WO2005032390A1
Application number: PCT/CH2004/000598
Authority: WO
Inventors: Patrick Pittet
Original assignee: Ap Technologies Sa
Priority date: 2003-10-09
Filing date: 2004-09-22
Publication date: 2005-04-14

Abstract

The invention relates to the use of a six-dimensional (position and orientation) position-tracking device which is suitable for use in robot-assisted surgery or in robot-assisted therapy. The invention consists in equipping the robotic arm with an optical system for measuring distance or distance profile and moving said system with the robot such as to collect a sufficient number of measurement points in order to determine precisely the position and orientation of an anatomical structure in relation to the robot and in relation to examinations of said structure performed earlier or currently underway. In addition, the virtual sensor thus produced can be used for other operations, such as collecting points for the analysis of the profile or the surface of an anatomical structure, detecting the movements of an anatomical structure or calibrating tools, components and systems used during the above procedure.

Description

Device for robot-assisted medical treatment

The present invention relates to a localization device and the associated implementation method for robot-assisted surgery and robot-assisted therapy.

The main objective of robotic assistance for the surgical or therapeutic gesture is to increase the precision and repeatability of the execution of this gesture by providing good traceability of the intervention. It can also allow the carrying out of complex gestures and prohibit dangerous gestures.

To obtain the desired precision and repeatability, the robotic assistance must implement localization means adapted to identify the patient in relation to the six dimensions of the space (in position and in orientation) during the intervention. to the robot and to be able to readjust exams (containing spatial information) carried out before or during intervention.

This localization problem goes beyond the framework of robotic assistance and is common to all computer-assisted surgery and therapy systems. These last two fields will be used to make a quick state of the art in the matter.

A first family of localization methods uses the imaging means available during the intervention. For example, mention may be made in computer-assisted surgery of mapping by fluoroscopy, or by using an ultrasound probe as described in the Sofamor Dane Holdings patents. (US-6477400), Surgical Navigation Technologies Inc (US-6470207) and Varian Médical Systems Inc (US-6549802). When a three-dimensional radiological system such as the intraoperative computed tomography (CT) scanner, the open magnetic resonance imager (open TRM) or the 3D fluoroscope is available during the intervention, the localization and registration of the patient's examinations can be reduce to mathematical and image processing operations.

There is another family of localization methods which implements a specific localization technology. Many systems are based on an optical triangulation principle using several cameras to locate locating elements or probes equipped with light-emitting diodes or reflective markers, as described for example in the Northern Digital Inc. patent (US-6061644). An original process using this technology is described by Raabe et al in the article "Laser Surface Scanning for patient registration in intracranial image-guided surgery" (Neurosurgery, Vol. 50, No. 4, pp. 797-803, April 2002) and in the patent Brainlab AG (EP-1142536A1). Other systems use electromagnetic technologies as described for example in patent Surgical Navigation Technologies I c (US-6381485). Still other systems use ultrasonic time of flight measurements as described in the patent of Integrated Surgical Systems SA and Fischer-Schnappauf-Stockmann Gbr (US 6,167,292). There are also solutions using electromechanical technology as described for example in the patent Integrated Surgical Systems Inc. (US-5806518).

There are also positioning systems based on two-dimensional or three-dimensional contactless optical distance measurements, such as the system for matching the patient with his tomo-scintigraphic and MRI examinations by laser scanning described by Philippe Cinquin in the article "Computer-assisted medical and surgical gestures and care unit of the future" (Informatique et Santé -Volume 7 - Springer Verlag France 1994) or the procedure for surgery guided by the image of the liver described by D. Cash et al . in the article "Fast, accurate surface acquisition using a laser range scanner for image-guided liver surgery" (SPIE Medical Imaging 2002 proceedings: Visualization, Display, and Image-guided Procedures, 2002) or the system described in the patent Massachusetts General Hospital Corporation (US 4,480,920). In the article "Computer Assisted Orthopedic and Trauma Surgery: State of the art and future perspectives" by NWL Schep et al. (Injury, Int. J. Care Injured 34 (2003) 299-306), a recent system of surface mapping by measuring non-contact optical distance is reported by manually moving a laser telemetry cell and locating at all times to the cell using a position sensor. Quite similarly and for another field of application, the patent application of Farcy et al. (W01 / 035849A) describes the use of a laser profilometer in the context of computer-assisted surgery which aims to obtain “augmented reality” or “surgically modified images” by using external videoendoscope positioning sensors and of the laser profilometer.

In the context of robot-assisted surgery and therapy, the patent Integrated Surgical Systems Inc (US 6,033,415) offers a solution for carrying out the matching. between the image of a long bone and a surgical robot. In the context of these applications, it may be interesting to exploit the fact that the robotic arm is capable of positioning and orienting a tool according to the six degrees of freedom of space to produce a six-dimensional localization system with from a measurement in one direction of space. Such a device is implemented in the patent Integrated Surgical Systems Inc (US 5,806,518). A probe is mounted on the robot's effector and comes to palpate locating elements (screws for example), at the time of the feeler-locating element contact, the position of the probe end is calculated from the geometric model of the robot , articular coordinates of the robotic arm and elements for manufacturing and calibrating the probe, an effort sensor associated with this probe makes it possible to guarantee the repeatability of detection of the probe-locating element contact. Another patent Integrated Surgical Systems Inc (US6033415A) describes an embodiment aiming at the correspondence between an anatomical structure and the robot by direct digitization of the surface of this structure. According to this patent, a mechanical palpation device is used to digitize the structure, which requires contact with said structure.

The present invention aims to exploit all the resources of the robot to achieve a simple, reliable, precise, efficient localization system compatible with the requirements of surgical and therapeutic applications. An object of the invention is to provide a device and a method for locating an anatomical structure in the frame of reference associated with the robot by measuring distance or distance profile to determine the matrix of passage between the frame of reference associated with this anatomical structure. and the one associated with the robot. Another object of the invention is to propose such a device and method for locating an anatomical structure for the registration of examinations carried out before or during intervention with the current position and orientation of this anatomical structure. Another object of the invention is to propose such a localization device and method for performing calibration or verification operations of tools, components or mechanical and electromechanical systems used in robot-assisted surgery or in robot-assisted therapy. . Another object of the invention is to propose such a localization device and method for detecting the movement of an anatomical structure during intervention. Another object of the invention is to propose such a localization device and method for performing a profile or surface analysis of an anatomical structure before, during or at the end of the intervention. An advantage of the invention is that the active part of the device is carried by the robotic arm and that it does not come into contact with the patient. The distance or distance profile measurement is carried out by non-contact optical measurement either directly on the anatomical structure concerned or on a passive structure rigidly fixed to the latter. Thus the active part of the device can be seen as a virtual contactless probe. For the applications concerned (therapeutic and surgical), this characteristic of the invention makes it possible to increase safety by not generating patient leakage currents for example, by facilitating implementation in a sterile environment and avoiding the risks of contamination. cross; Another advantage of the invention is that the combination of the robot and the optical distance measuring cell constitutes an autonomous system which performs the distance measurement in a frame of reference intrinsically associated with the robot, thereby increasing the precision and reliability of the localization of the anatomical structure in relation to the robot. Another advantage of the invention is that it can exploit the intelligence of the robot to optimize the localization of the anatomical structure both in terms of localization precision and in aspects such as the time required for localization. In particular, information known a priori could be introduced for this optimization such as the geometric knowledge of the test patterns and locating elements (manufacturing or calibration data) or even the knowledge of the surface geometry of the anatomical structure calculated from the examinations available on this structure. In particular, for surface matching, the collection of highly discriminating points is favored on the anatomical surface rather than a regular mesh of the surface. Another advantage of the invention is that it is based on a simple, well-controlled technology and a measurement of distance or profile of distance, technology 1 widely used for several years in dimensional control in industry. Consequently, the cost and the reliability of implementing the invention are optimized. Another advantage of the invention is that the optical measurements are made a few decimeters from the patient, in an optimized work volume with the system for transmitting and detecting the optical signal on board the robotic arm. This characteristic of the invention makes it possible to limit the risks of masking the line of sight, frequently observed with the optical localization systems working on a larger work volume, the detection system being fixed relative to the reference of the intervention room. For the same reasons, the risks of dazzling the cell are reduced. As a result, the implementation of the invention is simplified and made more robust. Another advantage of the invention is to use the same distance measurement cell or distance profile to cover aspects as different as the mapping of the robot to the patient, registration of clinical examinations, verification and calibration of tools or components and collection of traceability data. This characteristic of the invention contributes to improving the degree of integration of the robotic assistance system.

To achieve these objects, the present invention provides a measurement device comprising an integrated optical distance or distance profile measurement cell and mechanical and electrical interface elements allowing it to be mounted on the effector of the robotic arm. This cell behaves like a virtual probe whose position of the virtual end can be calculated in the robot's frame of reference from the geometric model of the latter, its joint coordinates, the distance measurement provided by the cell and elements for manufacturing or calibrating the measuring device. The geometry of the end of this virtual probe is considered to be punctual in the case where a cell. distance measuring device is used or planar with a shape corresponding to the measured profile in the case where a distance profile measuring cell is used. The present invention provides a method which consists in moving this device with the robotic arm to collect several measurement points. According to an embodiment of the present invention, said virtual probe is used to directly locate the surface of an anatomical structure; this virtual probe being moved by the robotic arm to acquire, that is to say locate, in the base frame of reference of the robot various points of the anatomical surface. According to one embodiment of the present invention, the matching of the points acquired with the surface of the anatomical structure extracted from the three-dimensional examinations is used for the registration of these examinations during intervention. According to an embodiment of the present invention, the location of an anatomical structure is carried out by means of a test pattern, the test pattern being a three-dimensional object rigidly fixed to the anatomical structure and whose geometric, mechanical and optical characteristics are optimized and known a priori by the robot to perform a quick and precise identification of this target, optical distance or distance profile measurements being carried out directly on this target. According to an embodiment of the present invention, the target is fixed on a support which is itself fixed to the anatomical structure; during examinations carried out before or during intervention, this same support receives instead of or in conjunction with the test pattern, a three-dimensional marking system compatible with the examination considered, the relative position and orientation of the system marking and test pattern are then integrated into the matching algorithm. . According to one embodiment of the present invention, the target is constituted by a plate comprising a relief pattern whose geometry is known a priori, and which allows, from a limited number of measurement points, to locate the target in the six dimensions of unambiguous space. According to one embodiment of the present invention, the target is constituted by a planar structure having a discriminating contour which allows, from a limited number of measurement points, to locate the target in the six dimensions of the space without ambiguity . According to an embodiment of the present invention, the identification is carried out by detection of at least three non-aligned elements rigidly fixed to the anatomical structure, these elements being in relief relative to the surface of the anatomical structure. According to one embodiment of the present invention, the identification is carried out by at least one axial element rigidly fixed to an anatomical structure and on which an extension can be mounted, from distance measurements with and without the extension, it is possible to determine both the position and the orientation of this axial element. According to an embodiment of the present invention, the measurements of distance or of profile of distances are used to detect the movement of an anatomical structure during intervention by direct measurement on this structure. According to an embodiment of the present invention, the measurements of distance or of profile of distances are used to detect the movement of an anatomical structure during intervention by measurement on a target rigidly fixed to this structure. According to an embodiment of the present invention, the measurements of distance or of profile of distances are used to detect the movement of an anatomical structure during intervention by direct measurement on one or more elements rigidly fixed to this structure and in relief in relation to its surface. According to an embodiment of the present invention, the distance or profile profile measurements are used to make a profile or surface analysis of an anatomical structure before, in progress or after intervention. According to one embodiment of the present invention, the distance or distance profile measurements are used for operations of calibration or verification of tools, components or electromechanical mechanical systems used in robot-assisted surgery or in assisted therapy. by robot.

These objects, characteristics and advantages, as well as others of the present invention, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures:

Figure 1 shows schematically a device carried by a robot implementing the principles of distance measurement by laser triangulation and / or by a defocusing technique, this on a bone structure; FIG. 2 illustrates a measuring device according to the present invention where the device is mounted on the terminal effector of the robot; FIGS. 3A to 3D illustrate different embodiments of the target according to the present invention; FIGS. 4A and 4B illustrate the measuring device which enhances a femur equipped with locating elements screwed or glued in relief relative to its surface; FIGS. 5A and 5B illustrate the measurement device acting on an axial locating element with its extension in the two associated measurement configurations; FIG. 6 represents the measuring device acting on an axial locating element with a plate and an indexing system allowing locating according to the 6 dimensions of the space without ambiguity.

The measuring device according to the present invention can be formed from an integrated distance measuring cell. This cell generally includes a laser diode, possible elements making the beam asymmetrical (in the case where a defocusing principle is used), optical components (lenses, diaphragms) and a detector. This detector can be produced from a strip or a CCD matrix, a strip or a CMOS matrix or from a strip-sensitive position detector (PSD), or from any other photosensitive matrix device. The measuring device includes a permanent or temporary mechanical connection system with indexing allowing a unique mounting, precise and repeatable measurement cell on the robotic arm. This device also includes an electrical connection system to supply the electrical voltages necessary for the polarization of the measurement cell and to allow the robot to recover the analog and / or digital signals corresponding to the distances measured.

It is possible to make the device by integrating a distance profile measurement cell which is based on the same principles as those described above, with the addition of optical elements allowing from the point laser beam to generate a planar beam. Measuring a profile instead of an isolated measurement increases the speed of localization.

The distance or distance profile measurement device can be produced by simply adding the electrical and mechanical interface elements to integrated distance measurement or distance profile cells available on the market.

To constitute a virtual probe from this measuring device, it is necessary to have the geometric characteristics of the measuring device mounted on the robotic arm. These characteristics can be accessible either from design and / or manufacturing data, dimensional measurements, or from the results of a calibration procedure, or from a combination of all of this information. Certain conventional calibration procedures in robotics, in particular pivot techniques, can be applied by considering the optical measurement axis as the last segment of the robotic arm. It is then necessary to determine the offset of the origin of this segment relative to the last articulation of the robotic arm, and also to determine the orientation of the axis of this segment relative to this articulation. It is also possible to use test patterns dedicated to calibration associated with methods such as that described in the article "From accurate range imaging sensor calibration to accurate model based 3D object localization" by Champleboux et al (Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition pp. 83-89, 1992). If the distance or distance profile measurement is carried out directly on an anatomical structure, it is possible to carry out both the mapping of the robot to the patient and the registration of examinations of this patient using for example ime of surface mapping methods described in the article "An algorithm overview of surface regsitration techniques for medical imaging ”by MA Audette et al (Médical Image Analisys 4 (200) 201-217).

In the case where the distance or distance profile measurement cannot be carried out directly on the surface of the anatomical structure of interest, for example in the case where it is not accessible in direct vision (masking by other structures, etc.), it is possible to use a localization target rigidly fixed to this structure. This target is generally a three-dimensional object of discriminating shape allowing an unambiguous localization according to the six degrees of freedom of space. However, it is possible to produce a flat test pattern, with a discriminating geometry contour. With the distance or distance profile measurement device, it is easy to detect this contour which corresponds to a distance discontinuity, even to a discrimination between value in and out of measurement range.

Another solution is to produce discriminating patterns in relief, these patterns can be obtained by simple machining methods such as drilling, milling, etc. FIGS. 3A to 3C respectively present planar patterns produced with a discriminating contour, with holes and with grooves.

It is also possible to produce a truncated pyramid pattern, with discriminating facet planes as illustrated in Figure 3D.

This target can be rigidly fixed to the anatomical structure of interest by means of an intermediate piece called a support. This support allows the unique, precise and repeatable mounting of the target and possibly of specific localization systems for the different examination methods. From the design, manufacturing, measurement and / or calibration data, it is possible to calculate the passage matrix between the frame of reference associated with the target and the localization systems considered. This passage matrix is used for the registration of the images. To facilitate the identification of the anatomical structure, when the latter does not for example have a sufficiently discriminating shape, it is possible to use punctual identification elements rigidly fixed to it according to a strongly discriminating distribution pattern as illustrated. in 1 es 4A and 4B. These stamping elements can be screwed or glued to the surface of the structure or to the surface of elements integral with this structure. It is possible, in this configuration, to replace one or more of these point marking elements with an axial mark comprising a base element and its extension, as illustrated in FIGS. 5A and 5B. The advantage of this solution is to limit the number of tracking elements to achieve a mapping according to the six degrees of freedom of space. Indeed, this type of locating element provides two-dimensional information, namely an origin and an axis. For this, a measurement is taken consecutively without and with the extension in place.

An alternative solution for these locating elements is given in FIG. 6. It is a screwed element comprising an indexing pin and a plate. It offers 1 possibility of carrying out from a single element and with limited precision, a complete location according to the 6 degrees of freedom of the space. This characteristic makes it possible to set up an algorithm for automatic search for the other tracking elements in order to increase the overall accuracy of matching.

All of these tracking elements must be produced in such a way that they also constitute marking elements on the examinations carried out. It is then possible to implement paired point matching algorithms such as those referenced in the article by Maintz et al "A survey of medical image registration" (Médical Image Analysis 2 (1) 1-36 1998 ) to perform both the mapping of the robot to the patient and the registration of patient exams.

The measurement device proposed in the present invention can be used to detect displacements of an anatomical structure during intervention. For this, a reference measurement is carried out at the start and renewed at the end of the mapping at different points on the surface or on different marking elements. This measurement is renewed during the intervention and compared to the reference measurement. If this new measurement deviates significantly from the reference measurement, a displacement of the anatomical structure relative to the robot is detected.

The measurement device proposed in the present invention can be used to make a profile or surface analysis of an anatomical structure. For this, we determine a mesh of the surface and we proceed to the corresponding scan of the structure with the measuring device moved by the robot. To facilitate the interpretation of the results, the points acquired can be structured in the form of an image. This functionality is particularly advantageous when the intervention includes a step of machining the anatomical structure, the surface condition of which can condition the clinical result, as is the case, for example, for osteotomies.

References cited in this document

US Patents: US-5,806,518: Method and system for positioning surgical robot.

US-6, 167,292: Registering method and apparatus for robotic surgery, and a registering device constituting an application thereof.

US-6,061,644: System for determining the spatial position and orientation of a body.

US-6,381,485: Registration of human anatomy integrated for electromagnetic localization. US-6,477,400: Fluoroscopic image guided orthopedic surgery system with intraoperative registration.

US-6,549,802: Seed localization system and method in ultrasound by fluoroscopy and ultrasound fusion.

US-4,480,920: Fringe pattern method and apparatus for producing X-ray dosage compensating filters

US 6,033,415: System and method for performing image directed robotic orthopedic procedures without a fiducial reference system

PCT WO 01/35849 Al: Secure videscopic apparatus with laser profilometer for computer-assisted surgery

European Patents: EP-1142536A1: Patient referencing in a medical navigation system using projected light points

Bibliographic references:

Raabe et al, "Laser Surface Scanning for patient registration in intracranial image-guided surgery", Neurosurgery, Vol. 50, No. 4, pp. 797-803, April 2002.

Philippe Cinquin, “Computer-assisted medical and surgical gestures and healthcare unit of the future”, Informatics and Health -Volume 7 - Springer Verlag France 1994. D. Cash et al, “Fast, accurate surface acquisition using a laser range scanner for image - guided liver surgery ”, Proceedings of the SPIE Medical Imaging 2002 conference: Visualization, Display, and Image-guided Procedures, 2002.

Champleboux et al, “From accurate range imaging sensor calibration to accurate model based 3D object localization”, Proceedings of the IEEE Congress Conference on Computer Vision and Pattern Recognition, 1992).

M Audette et al, "An algorithm o verview of surface regsitration techniques for medical imaging", Médical Image Analisys 4 (200).

Maintz et al "A survey of medical image registration", Medical Image Analysis 2 (1) 1-36 1998.

Schep NWL et al. "Computer Assisted Orthopedic and Trauma Surgery: State of the art and future perspectives", Injury, International Journal Care Injured 34 (2003) pp. 299-306. Numerical references used in the figures Robot Anatomical structure Laser Optical cell Referential of the robot CCD Mask / Lens Measuring device

Claims

claims

1. Device for surgery or robot-assisted therapy, consisting of a non-contact virtual probe comprising at least one optical system for measuring distance or distance profile, said device being adapted to be carried and moved by a robot so to be able to locate an object in position and in orientation from several measurement points, directly in a frame of reference intrinsically associated with said robot.

2. Device according to claim 1 comprising a target for locating an anatomical structure, the target being made up of one or more three-dimensional objects rigidly fixed to the anatomical structure and the geometric, mechanical and optical characteristics of which are optimized and known. a priori by the robot to perform a quick and precise location of this target, the optical distance or distance profile measurements being carried out directly on this target.

3. Device according to claim 2 wherein the target is fixed on a support itself adapted to be fixed to the anatomical structure, this same support being adapted to receive instead of the target or jointly with this target, a system of compatible three-dimensional marking of the examination considered, the relative position and orientation of the marking system and the target are then integrated into the matching algorithm.

4. Device according to claim 3 wherein the target formed by a plate comprising a relief pattern whose geometry is known a priori, and which allows from a limited number of measurement points a location of the target in six dimensions unambiguous space.

5. Device according to claim 3 wherein the test pattern constituted by a planar structure has a discriminating contour which allows from a limited number of measurement points an identification of the test pattern in the six dimensions of the space without ambiguity.

6. Use of the device according to claim 1 wherein the distance or distance profile measurement system is based on the principle of laser triangulation, de-focusing or on a combination of these two principles.

. Use of the device according to Claim 1, in which the location is performed by direct optical measurement on an anatomical structure, the three-dimensional coordinates of points on the surface of this structure are calculated from the various measurements acquired with the virtual probe and the articular coordinates of the robot. corresponding, the mapping with the examinations of this structure carried out before or during the intervention is carried out using a surface mapping algorithm.

8. Use of the device according to claim 1 wherein the identification is carried out by detection of at least three non-aligned elements rigidly fixed to the anatomical structure, these elements being in relief relative to the surface of the anatomical structure.

9. Use of a device according to claim 1, in which the identification is carried out by at least one axial element rigidly fixed to an anatomical structure and on which an extension can be mounted, from distance measurements with and without the extension, it is possible to determine both the position and the orientation of this axial element.

10. Use of a device according to claim 1 for detecting the movement of an anatomical structure during intervention by direct measurement on this structure.

11. Use of a device according to claim 1 for detecting the movement of an anatomical structure during intervention by measurement on a target rigidly fixed to this structure.

12. Use of a device according to claim 1 for detecting the movement of an anatomical structure during intervention by direct measurement on one or more elements rigidly fixed to this structure and in relief relative to its surface.

13. Use of a device according to claim 1 to make a profile or surface analysis of an anatomical structure in pre, per or post-operative.

14. Use of a device according to claim 1 for operations of calibration or verification of tools, components or electromechanical mechanical systems used in robot-assisted surgery or in robot-assisted therapy.